1. Field of the Invention
This invention relates to high performance overbased calcium salicylate greases, the preparation of these greases and intermediates. More particularly, this invention relates to a process of forming a non-Newtonian oil composition in the form of a grease comprising an overbased calcium salicylate and solid particles of colloidally dispersed calcium carbonate in the form of calcite which comprises heating overbased calcium salicylate, amorphous calcium carbonate, and a converting agent comprising a fatty acid of twelve to twenty-four carbon atoms in an oleaginous vehicle, and then adding sufficient carbon dioxide to complete the conversion of the amorphous calcium carbonate to calcite.
2. Description of Related Art
As pointed out in U.S. Pat. No. 4,560,489, thixotropic greases or grease-like overbased calcium sulfonate compositions have corrosion-inhibiting properties and have utility for a variety of uses such as, for instance, in automobile and truck body undercoating, and for various other purposes known to the art and are disclosed in various publications and patents, such as U.S. Pat. Nos. 3,242,079; 3,372,115; 3,376,222; 3,377,283; 3,523,898; 3,661,622; 3,671,012; 3,746,643; 3,730,895; 3,816,310; and 3,492,231. Such greases or grease-like compositions have gone into wide-spread use either as such, or mixed with other ingredients to produce compositions for use in a variety of environments and, generally speaking, they are characterized by reasonably good E.P. & Antiwear Properties, high dropping points, reasonably good resistance to mechanical breakdown and salt spray- and water-corrosion, thermal stability at high temperatures, and other desirable properties.
As is well known, greases are sold in various grades depending upon the softness of the grease. The softer the grease the more fluid it is. Typically, these greases are rated or graded on the basis of their worked cone penetration range. For example, greases sold under the designation grade zero have a cone penetration number from about 355 to 385, those having a cone penetration range of 310 to 340 are designated grade one, and the most widely sold greases have a cone penetration range of 265 to 295 and are designated grade two. The lower the grade of the grease the more relatively inexpensive oleaginous vehicle and the cheaper the grease. For the purposes of this invention, cone penetration is measured by the ASTM cone penetration test (D217). Penetration is the depth, in tenths of a millimeter, to which a standard cone sinks into the grease under prescribed conditions. Thus, higher penetration numbers indicate softer greases, since the cone has sunk deeper into the sample.
The greases disclosed in U.S. Pat. No. 4,560,489 can be prepared by one step or two step processes. In the one step process, neutral calcium sulfonate, hydrated lime, lubricating oil, a converting agent capable of converting amorphous calcium carbonate into crystalline calcium carbonate, and a catalyst suitable for promoting carbonation of the neutral calcium sulfonate, such as methanol, are carbonated to form a non-Newtonian highly overbased calcium sulfonate solution. Additional oil stock, lime, water, boric acid, and fatty acid are then added to complete the production of the overbased calcium sulfonate grease. In the two step process, a composition comprising a Newtonian highly overbased calcium sulfonate solution is first converted to a thickened intermediate non-Newtonian product by initial treatment thereof with a converting agent such as acetic acid, propionic acid, or an alcohol. Then, there is subsequently added thereto, at elevated temperatures, boric acid in admixture with, or dissolved or partially dissolved in, hot water, lime, or calcium hydroxide and the soap-forming aliphatic monocarboxylic or fatty acid such as a C12 to C24 acid. In both the one step and two step processes, the soap-forming aliphatic monocarboxylic acid or fatty acid containing from 12 to 24 carbon atoms is added to the non-Newtonian highly overbased calcium sulfonate solution containing calcium carbonate in the calcite form.
U.S. Pat. No. 5,308,514 discloses high performance overbased calcium sulfonate greases comprising up to about 28% by weight overbased calcium sulfonate, solid particles of colloidally dispersed calcium carbonate essentially in the form of calcite, a calcium soap of a fatty acid of twelve to twenty-four carbon atoms, and oleaginous vehicle wherein at a concentration of about 28% by weight overbased calcium sulfonate said greases have a worked cone penetration rating of less than about 295.
U.S. Pat. No. 5,338,467 discloses a process of forming a non-Newtonian oil composition in the form of a grease comprising an overbased calcium sulfonate and solid particles of colloidally dispersed calcium carbonate in the form of calcite which comprises heating overbased calcium sulfonate, amorphous calcium carbonate and a converting agent comprising a fatty acid of twelve to twenty-four carbon atoms in an oleaginous medium.
The disclosures of the foregoing are incorporated herein by reference in their entirety.